1. Field of the Invention
The present invention relates to a support structure for an operating pedal of a vehicle.
2. Description of the Related Art
A conventionally known support structure for an operating pedal of a vehicle, such as a brake pedal or a clutch pedal, is such that a foot-operated pedal unit with a tread plate provided at a lower end is pivotably supported by a pedal bracket which is fixed to a dash panel, allowing a driver to pivot the operating pedal along a longitudinal direction of the vehicle. This structure permits the pedal unit which is supported by the pedal bracket at an upper end via a laterally extending first pivot shaft to pivot along the longitudinal direction of the vehicle when the driver presses down on the tread plate by the foot. In the design of this kind of operating pedal support structure, it is required that the pedal unit will not be greatly displaced rearward in the event of a collision (especially in a frontal collision) of the vehicle for protecting the driver's lower limbs.
An arrangement to meet the aforementioned requirement is described in Japanese Unexamined Patent Publication No. 2005-510785, for example. According to the Publication, a pedal bracket is pivotably supported by means of a laterally extending second pivot shaft and there is provided a pivotable lever which pivots on the second pivot shaft and goes into contact with a side member of a vehicle body in the event of a collision of the vehicle. In this arrangement, a first pivot shaft (pedal supporting shaft) is forcibly displaced rearward in the event of a collision and, as a consequence, a pedal unit and a tread plate are displaced in a frontward direction of the vehicle body.
Japanese Patent No. 3269372 shows another arrangement aimed at meeting the aforementioned requirement. According to the Patent, a support structure for an operating pedal is such that a pivot shaft of a pedal unit is displaced in a rearward direction of a vehicle relative to a tread plate provided at a lower end of the pedal unit in the event of the vehicle collision, the support structure including a spring which serves as biasing means for retaining the pivot shaft at an upper initial position.
On the other hand, European Patent Publication No. EP0659615 proposes a support structure for an operating pedal, in which arms of a pedal bracket holding a pivot shaft of a pedal unit deform and become separated form each other along a lateral direction of a vehicle body in the event of a vehicle collision so that the pedal unit is disengaged from the pedal bracket.
In the aforementioned arrangement of JP No. 2005-510785, the supporting shaft of the pedal unit is normally supported by the pivotable lever, so that an external force exerted on the pedal unit, for instance, tends to produce irregular movements of the pivotable lever, potentially causing the pedal unit to be supported in an unstable state and jeopardizing the driver's feeling of pedal operation.
In the aforementioned arrangement of JP No. 3269372, the pivot shaft pivotably supporting the pedal unit is likely to produce loose vibratory movements as a result of extension and compression of the spring. This makes it difficult to properly maintain comfortable operability of the pedal unit.
Also, the operating pedal support structure of EP0659615 has a problem that it is difficult to disengage the pedal unit from the pedal bracket in a reliable fashion if the pedal unit becomes aslant when the arms of the pedal bracket deform and become separated apart in the event of a vehicle collision.
In addition to solving the aforementioned problems of the prior art, it is required for an operating pedal support structure to prevent the pedal unit from becoming unexpectedly displaced downward to a great extent when a large downward external force is exerted on the pedal unit as a result of depression of the pedal by the driver.